1. Field of the Invention
The present invention relates to a method and apparatus for welding a reinforcing tape formed of a synthetic resin to a portion to which the separable bottom stop of a slide fastener chain is to be attached over the core portion of a fastener tape and a main tape portion by ultrasonic heating.
2. Description of the Related Art
A space portion (a tool lacking portion) for attaching an upper stopper and a separable bottom stop is intermittently formed in a fastener chain for a slide fastener having the separable bottom stop. The separable bottom stop is attached to the space portion. Before the separable bottom stop is attached, a reinforcing tape piece formed of a synthetic resin is usually bonded to the separable bottom stop attachment portion of the fastener chain, thereby giving a reinforcement.
The reinforcing tape piece is bonded in such a configuration as to hold opposed tape side edges in the space portion of the fastener chain, and a core cord is woven into each of the opposed side edges of the fastener chain and they are therefore thick. When the whole reinforcing tape piece is simultaneously bonded to a thick portion and a flat portion by pressure, wrinkles and air bubbles to cause a separation remain. Furthermore, the bonding configuration of the reinforcing tape piece is apt to be broken. In order to solve the problem, the reinforcing tape piece is bonded and integrated in two stages as described in JP-B-62-54001 and JP-B-63-40085, for example.
In JP-B-62-54001, for example, a reinforcing tape piece is provided orthogonally to the space portion of a fastener chain for each transfer stop period of each fastener chain, the upper and lower edges of the reinforcing tape piece are bent and the reinforcing piece is held from the inside and outside of the space portion. A core cord portion held by the reinforcing tape piece and a tape portion in the vicinity thereof are then pressurized and heated from the inside and outside to bond a part of the reinforcing tape piece to the core cord portion, and subsequently, the reinforcing tape piece provided adjacently to the bonding region and the non-bonding region of the tape portion are pressurized and heated from the inside and outside to completely bond and integrate both of them.
In JP-B-63-40085, moreover, a reinforcing tape piece having a constant dimension which is formed of a thermoplastic synthetic resin is caused to abut across the opposed edges of left and right fastener tapes from both upper and lower sides of a reinforcing tape attachment portion in the space portion of a slide fastener chain. The reinforcing tape piece is interposed by pressure between an ultrasonic horn and an anvil. The ultrasonic horn includes a straight concave groove in a portion corresponding to the core cords of the left and right fastener tapes and a cutting blade on the outer end of the core cord. The anvil includes a straight concave groove in a portion corresponding to the core cord and a cutting blade on the outer end of the core cord in the same manner. Then, an ultrasonic processing is carried out and the reinforcing tape piece is welded to the outer periphery of the core cords of the left and right fastener tapes and a tape portion in the vicinity thereof, and at the same time, the reinforcing tape piece provided between the opposed core cords is cut out and the residual portion of the reinforcing tape piece is then welded to the both faces of each of the left and right fastener tapes by pressurization and heating.
On the other hand, for example, JP-B-2-35661 and JP-A-63-315223 have disclosed the control method for welding, which utilizes an ultrasonic vibration in which the temperature of a horn is detected to control the amplitude of the ultrasonic vibration of the horn. In the control method, control is carried out such that a temperature detecting element, for example, a thermistor is attached to a presser tool or a receiving portion to detect a temperature, and the amplitude of the ultrasonic vibration is increased if the temperature is low and the amplitude is reduced if the temperature is high. Moreover, as disclosed in JP-A-62-140823 and JP-A-5-299480, for example, the temperature of an ultrasonic horn including a heating device such as a heater is detected and the heating device is controlled to maintain the temperature of the horn to be constant.
According to each of the bonding (welding) techniques for the reinforcing tape piece disclosed in JP-B-62-54001 and JP-B-63-40085, the core cord portion of a fastener tape and a tape portion in the vicinity thereof is are welded to be held by a reinforcing tape piece in a first stage and the residual non-welding region of the reinforcing tape piece is welded to the fastener tape in a second stage so that integration is carried out in two stages. In JP-B-62-54001, development has been carried out on the assumption that the reinforcing tape piece is bonded to the space portion of the fastener chain through an adhesive in the two stages, and the bonding (welding) can be carried out by heating and welding using a heater if a thermoplastic synthetic resin material is used for the reinforcing tape piece. On the other hand, in JP-B-63-40085, ultrasonic welding means is employed in a first stage and heating and welding means using an ordinary heater is employed in a second stage.
As described above, it is necessary to strictly control a heating temperature and a processing time for the welding using the heater. If either of them is lessened, a bonding failure is caused. If either of them is excessive, the reinforcing tape piece enters the fastener tape in a fusing state. Consequently, the fastener tape is caused to be fragile and excessively rigid so that it might be bent or damaged easily. In addition, the welding using heater heating takes a longer time for the processing as compared with general ultrasonic welding. As disclosed in JP-B-63-40085, for example, in the case in which a welding step using the heater heating is to be carried out after the ultrasonic welding, a difference is made on the processing time. If the heating temperature of the heater is increased to match the difference in the processing time with an ultrasonic welding time in order to prevent a separation from being caused by a bonding failure, excessive heating is generally apt to be caused so that a welding portion becomes rigid and fragile. In the case in which the heating is carried out by the heater, furthermore, an air bubble is easily generated between a core cord portion and a main tape portion.
On the other hand, in the case in which a reinforcing tape piece is to be bonded to the space portion of a fastener tape of this kind, the holding configuration of the reinforcing tape piece is to be usually arranged uniformly by molding as well as welding in order to decide the configuration of the core cord portion. On the other hand, it is sufficient that the bonding of the reinforcing tape piece to the main tape portion of the fastener tape is simply carried out without changing a surface configuration thereof as long as a bonding strength is maintained. In the welding to be carried out by the ultrasonic heating under the proper conditions, only a welded surface is fused and bonded by internal heating. Consequently, a processed surface is finished finely without a deformation.
If the core cord portion of the fastener tape and the main tape portion are to be welded at the same time by using a single ultrasonic horn and a single anvil as disclosed in JP-A-5-299480, an ultrasonic oscillation is carried out with the same amplitude in an equal time for the core cord portion of the fastener tape and the main tape portion during the welding. On the other hand, it is desirable that the pressing force of the molded surfaces of the ultrasonic horn and the anvil for the core cord portion of the fastener tape at time of the ultrasonic vibration should be smaller than the pressing force of the molded surfaces of the ultrasonic horn and the anvil for the main tape portion of the fastener tape because the pressing and molding is carried out at the same time as described above.
However, conventionally, the pressed surfaces of the ultrasonic horn and the anvil are set to be lightly held with respect to the fastener tape and are set to be strongly pressed in order to obtain a predetermined sectional configuration with respect to the core cord portion. When the ultrasonic welding is carried out with the same amplitude in an equal time with such a configuration of the pressed surface, an excessive energy is given to the core cord portion having the great pressing force. As a result, the reinforcing tape piece portion of the core cord portion is greatly fused so that the core cord portion becomes rigid and fragile in many cases.
The invention has been made to solve the conventional problems and has an object to provide a welding method in which a core cord portion and a main tape portion are welded by ultrasonic heating under proper conditions respectively in order to weld a reinforcing tape piece to the space portion of a fastener chain and a welding apparatus therefor.
The object can be attained effectively by an ultrasonic welding method for welding a reinforcing tape to a fastener tape having a main structure according to a first aspect of the invention.
The structure is characterized by a method for welding a reinforcing tape piece formed of a synthetic resin to a separable bottom stop attachment portion of a slide fastener chain by ultrasonic heating over a core portion and a main tape portion in a fastener tape, including the steps of setting a welding time and/or an amplitude which are/is suitable for welding the reinforcing tape piece to the core portion and the vicinity of the core portion, and a welding time and/or an amplitude which are/is suitable for welding the reinforcing tape piece to the main tape portion, and welding the reinforcing tape piece to the core portion and the vicinity of the core portion and welding the reinforcing tape piece to the main tape portion based on the welding time or the amplitude which is set.
As fifth and ninth aspects, moreover, the invention related to a suitable welding apparatus for carrying out the invention related to the method is characterized by an ultrasonic horn and an anvil having outer configurations of the core portion and the main tape portion in the fastener tape in the separable bottom stop attachment portion of the slide fastener chain, and a control portion connected to an ultrasonic vibrator connected to the ultrasonic horn and having a time and/or amplitude setting portion capable of setting a suitable welding time and/or amplitude for welding the reinforcing tape piece to the core portion and the vicinity of the core portion and a suitable welding time and/or amplitude for welding the reinforcing tape piece to the main tape portion respectively. In the invention, accordingly, the expected object can be attained by only setting one of the welding time and the amplitude, and both the welding time and the amplitude can also be set at the same time.
With such a structure, the reinforcing tape piece and the core portion and the main tape portion in the fastener tape in the separable bottom stop attachment portion of the slide fastener chain are subjected to the ultrasonic welding under proper conditions respectively. Therefore, the core portion can be prevented from being fragile and rigid and the main tape portion can be prevented from being welded insufficiently, and furthermore, the reinforcing tape piece can be prevented from separating from the main tape portion during the use of the slide fastener. Moreover, the ultrasonic welding is carried out under the proper conditions. Therefore, an air bubble generated on the welded surface is efficiently removed out by an ultrasonic vibration. Consequently, the air bubble can be prevented from remaining on the welded surface so that finishing can be carried out with a high transparency.
As a second aspect of the invention, it is preferable that the welding time or amplitude which is suitable for welding the reinforcing tape piece to the core portion and the vicinity of the core portion should be set to be smaller than the welding time or amplitude which is suitable for welding the reinforcing tape piece to the main tape portion. Whether the ultrasonic welding is carried out properly depends on the welding time, the pressing force and the amplitude. As described above, the core portion is to be molded to have a desirable section simultaneously with the welding of the reinforcing tape piece. Therefore, the pressing force to be applied to the core portion is greater than the pressing force to be applied to the main tape portion. For example, in the case in which the welding times for the core portion and the main tape portion are set to be equal to each other, the amplitude of the core portion is set to be smaller corresponding to the greater pressing force. In the case in which the amplitudes are set to be equal to each other, moreover, the welding time of the core portion is set to be shorter than the welding time of the main tape portion.
Third and fourth aspects of the invention are directed to the welding method wherein the welding of the reinforcing tape piece to the core portion and the main tape portion in the vicinity of the core portion and the welding of the reinforcing tape piece to the main tape portion are carried out independently and separately or the reinforcing tape piece is welded to the main tape portion and the main tape portion and the reinforcing tape piece are successively welded to the core portion and the main tape portion in the vicinity of the core portion at the same time.
Accordingly, as a sixth aspect of the invention, for example, the ultrasonic horn is formed by a single horn and the anvil is provided with a first anvil for supporting a pair of core portions and a pair of main tape portions in the vicinity of the core portions in the slide fastener chain and a pair of second anvils for supporting the main tape portions to be operable independently each other.
In this case, as a seventh aspect of the invention, for example, it is desirable that the control portion should further include a sequence control portion for moving the second anvil to a welding position to hold the reinforcing tape piece and the main tape portion together with the ultrasonic horn and for operating the ultrasonic vibrator for the set time to heat and weld the reinforcing tape piece and to then move the second anvil to a standby position and for moving the first anvil to a welding position to hold the reinforcing tape piece, the pair of core portions and the main tape portions in the vicinity of the core portions together with the ultrasonic horn and for operating the ultrasonic vibrator for the set time to heat and weld the reinforcing tape piece and to then move the second anvil to the standby position.
As an eighth aspect of the invention, for example, the control portion can further include a sequence control portion for moving the second anvil to a welding position to hold the reinforcing tape piece and the main tape portion together with the ultrasonic horn and for operating the ultrasonic vibrator for the set time to move the first anvil to the welding position in the middle of heating and welding for the reinforcing tape piece and to hold the reinforcing tape piece, the pair of core portions and the main tape portions in the vicinity of the core portions together with the ultrasonic horn, thereby heating and welding the reinforcing tape piece in a residual operating time together with the main tape portion and then moving the first and second anvils to the standby position.
More specifically, according to the seventh aspect of the invention, the welding of the reinforcing tape piece to the main tape portion and the welding of the reinforcing tape piece to the core portion and the main tape portion in the vicinity of the core portion are carried out separately in accordance with each set time. According to the eighth aspect of the invention, the welding of the reinforcing tape piece to the main tape portion and the welding of the reinforcing tape piece to the core portion and the main tape portion in the vicinity of the core portion are carried out continuously by utilizing a difference between the set times.
In the case in which the control portion includes the amplitude setting portion, as a tenth aspect of the invention, the ultrasonic horn is formed by a single horn and the anvil is provided with a first anvil for supporting a pair of core portions and a pair of main tape portions in the vicinity of the core portions in the slide fastener chain and a pair of second anvils for supporting the main tape portions to be operable independently each other. The control portion further includes an operation indicating portion for operating an ultrasonic horn with the corresponding set amplitude when holding the reinforcing tape piece, the pair of core portions and the main tape portions in the vicinity of the core portions by the ultrasonic horn and the first anvil, and for operating the ultrasonic horn with the corresponding set amplitude when holding the reinforcing tape piece and the main tape portion between the ultrasonic horn and the second anvil. In this case, the single horn is operated with a change into each preset amplitude and the first or second anvil is operated to the welding position corresponding to the operating amplitude of the horn, thereby sequentially carrying out the welding of the reinforcing tape piece to the main tape portion and the welding of the reinforcing tape piece to the core portion and the main tape portion in the vicinity of the core portion.
As an eleventh aspect of the invention, moreover, the ultrasonic horn includes a first horn for exciting the core portions and the main tape portions in the vicinity of the core portions in the slide fastener chain and a second horn for exciting the main tape portion. The anvil is provided with a first anvil opposite to the first horn and a second anvil opposite to the second horn to be operable independently each other, and the control portion further includes an operation indicating portion for operating an ultrasonic horn with the corresponding set amplitude when holding the reinforcing tape piece, the pair of core portions and the main tape portions in the vicinity of the core portions by the first horn and the first anvil, and for operating the second horn with the corresponding set amplitude when holding the reinforcing tape piece and the main tape portion between the second horn and the second anvil.
More specifically, according to a tenth aspect of the invention, the single horn is operated in accordance with the two preset amplitudes and the first or second anvil is moved according to each set amplitude, and the welding of the reinforcing tape piece to the main tape portion and the welding of the reinforcing piece to the core portion and the main tape portion in the vicinity of the core portion are carried out separately in accordance with each set time. According to a eleventh aspect of the invention, the reinforcing tape piece, the core portion and the main tape portion in the vicinity of the core portion are welded to each other with the set amplitude between the first horn and the first anvil which are operated with the set amplitude, and the reinforcing tape piece and the main tape portion are welded to each other between the second horn and the second anvil which are operated with different set amplitudes.